Information Notice 1987-19, Perforation and Cracking of Rod Cluster Control Assemblies

Perforation and Cracking of Rod Cluster Control Assemblies

ML031140513
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	04/09/1987
From:	Jordan E NRC/IE
To:
References
IN-87-019, NUDOCS 8704080095
Download: ML031140513 (7)

SSINS No.: 6835 IN 87-19 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 April 9, 1987 IE INFORMATION NOTICE NO. 87-19: PERFORATION AND CRACKING OF ROD

CLUSTER CONTROL ASSEMBLIES

Addressees

All Westinghouse nuclear power pressurized-water reactor (PWR) facilities

holding an operating license or a construction permit.

Purpose

This notice is provided to inform recipients of a potentially significant

safety problem that could result from the perforation and cracking of the rod

cluster control assemblies (RCCAs) in Westinghouse PWRs. It is expected that

recipients will review the information for applicability and consider action, as appropriate, to preclude a similar problem from occurring at their facili- ties. However, suggestions contained in this information notice do not consti- tute NRC requirements; therefore, no specific action or written response is

required.

Description of Circumstances

An estimate that was intended to be conservative indicated that the RCCAs would

last for at least 15 years before the absorber cladding, a thin tube, would

show excessive thinning as a result of sliding wear. These components were

inspected at Point Beach Nuclear Plant, Unit 2, in 1983 after 13 years of

operation. As a result of this inspection Point Beach reported on August 18,

1983 that sliding wear was minor, but one control rod had a 2-in. crack near

the tip of the rod and severe fretting wear had occurred on several tubes.

Subsequent inspections at the Kewaunee and Haddam Neck nuclear power plants, which have been in operation for more than 12 years, confirmed the fretting

wear. In addition, Haddam Neck reported tube cracking in 32 of 47 RCCAs.

In the event of a breach of the tubing resulting from wall thinning, perfora- tion, or cracking, the immediate effect is the introduction of activation

products from the neutron absorber material into the reactor coolant. Although

there are large margins, another concern is the potential reduction in shutdown

margin and negative reactivity worth.

814809 .

- IN 87-19 April 9, 1987 Discussion:

Each RCCA contains 16 rods. The rods at Point Beach, Kewaunee, and Haddam Neck

were constructed with an outer tube of 0.019-in.-thick 304 stainless steel that

retains the absorber material (80% silver, 15% indium, 5% cadmium). Some newer

plants use hafnium as the absorber material, while others use boron carbide

surrounded by a 0.038-in.-thick tube. The control RCCAs are inserted or

withdrawn to compensate for various reactivity changes during operation of

the reactor and can trip to provide shutdown capability. The shutdown RCCAs

are fully withdrawn from the core when the reactor is critical.

At Kewaunee, marks of fretting wear about 1 inch in length, were found adjacent

to the guide blocks that position the rods when the RCCAs are in their withdrawn

position. The 1-in.-thick stainless steel blocks are spaced on 12-in. centers

and each rod in the cluster passes through all eight of the blocks. At Point

Beach the tubing wore in two modes: fretting and sliding of the rods over the

guide blocks during rod motion. Five RCCAs at Haddam Neck had wall thinning

resulting from fretting and four of these were actually wearing into the

absorber material. All of the others had fretting wear, but to a lesser

extent.

The fretting resulted from flow-induced vibratory contact between the rods and

the guide blocks during long periods of steady-state power operation. Vibration

is hydraulically induced by flow of the reactor coolant; therefore it is a

continuous process when the reactor coolant pumps are in operation. According

to Westinghouse Electric Corp. fretting wear encompassed one-third of the

circumference of the rod and the depth varied with the amount of time the

RCCAs were in the withdrawn position.

At Point Beach significant number of short hairline cracks at the lower extremity

of the tubing were observed near the end plug region of the rod. The cracks

extended axially for 4 in. and penetrated the stainless tubing, exposing the

absorber material. No circumferential cracks were found. Examination of the

cracks showed that irradiation-induced swelling of the absorber was the principal

cause of tensile stress in the cladding, which resulted in cracking after

substantial irradiation.

Where excessively worn rods were found, they have been replaced. While the

issue is being studied by NRC and the industry, several licensees have been

given approval to slightly change the position of the fully withdrawn RCCA in

order to distribute the wear among different locations on the tubing. Westing- house Electric Corp. reported that an increase in the amount of the silver

isotope, Ag-110m in the reactor water is a reliable indication of exposure of

absorber material due to cracking or fretting wear.

- IN 87-XX

April, 1987 notice.

No specific action or written response is required by this information

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

Edward L. Jordan, Director

Division of Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Paul Cortland, IE

(301) 492-4175 Attachment: List of Recently Issued IE Information Notices

• See Previous Concurrences

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02/18/87 03/02/87 03/02/87 02/26/87 03/04/87 03/05/87

Attachment 1 IN 87-19 April 9, 1987 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

87-18 Unauthorized Service on 4/8/87 All NRC licensees

Teletherapy Units by authorized to use

Nonlicensed Maintenance radioactive material

Personnel in teletherapy units

87-17 Response Time of Scram 4/7/87 All GE BWR facilities

Instrument Volume Level holding an OP or CP

Detectors

87-16 Degradation of Static IIOU 4/2/87 All LWR facilities

Ring Pressure Switches holding an OL or CP

87-15 Complaince with the Posting 3/25/87 All power reactor

Requirements of Subsection facilities holding

223b of the Atomic Energy a CP and all firms

Act of 1954, as Amended supplying components

or services to such

facilities

87-14 Actuation of Fire Sup- 3/23/87 All power reactor

pression System Causing facilities holding

Inoperability of Safety- an OL or CP

Related Ventilation Equipment

86-106 Sup. 2 Feedwater Line Break 3/18/87 All power reactor

facilities holding

an OL or CP

87-13 Potential for High Radiation 2/24/87 All power reactor

Fields Following Loss of facilities holding

Water from Fuel Pool an OL or CP except

Fort St. Vrain.86-106 Sup. 1 Feedwater Line Break 2/13/87 All power reactor

facilities holding

an OL or CP

87-12 Potential Problems With 2/13/87 All power reactor

Metal Clad Circuit Breakers, facilities holding

General Electric Type AKF-2-25 an OL or CP

87-11 Enclosure of Vital Equipment 2/13/87 All power reactor

Within Designated Vital facilities holding

Areas an OL or CP

OL = Operating License

CP = Construction Permit

IN 87-XX

March, 1987 during

inserted or withdrawn to compensate for various reactivity changes The

operation of the reactor and can trip to provide shutdown capability. is critical.

shutdown RCCAs are fully withdrawn from the core when the reactor

guide blocks

At Kewaunee, marks of fretting wear were found adjacent to theposition. The 1- that position the rods when the RCCAs are in their withdrawn and each rod in

in.-thick stainless steel blocks are spaced on 12-in. centers Beach the tubing

the cluster passes through all eight of the blocks. At Point during rod motion

wore in two modes: sliding of the rods over the guide blocks from fret- and fretting. Five RCCAs at Haddam Neck had wall thinning resulting material. All

ting and four of these were actually wearing into the absorber

of the others had wear, but to a lesser extent.

contact

The tubing was worn by fretting resulting from flow-inducedofvibratory

steady-state power

between the rods and the guide blocks during long periods coolant;

the reactor

operation. Vibration is hydraulically induced by flow of pumps are in

therefore it is a continuous process when the reactor coolant

operation. In general, fretting wear was 1/2-in. long and encompassed

with the amount of

one-third of the circumference of the rod. The depth varied depth of

time the RCCAs were in the withdrawn position. The worst measured

of tubing thickness.

tubing penetration from fretting wear was 65 percent

of the

A significant amount of short hairline cracks at the lower extremity

cracks extended

tubing was observed near the end plug region of the rod. The

axially for 4 in. and penetrated the stainless tubing. No circumferential

cracks were found. Examination of the cracks showed that irradiation-induced

in the

swelling of the absorber was the principal cause of tensile stress

cladding, which resulted in cracking after substantial irradiation.

notice.

No specific action or written response is required by this information

Regional

If you have any questions about this matter, please contact the

Administrator of the appropriate regional office or this office.

Edward L. Jordan, Director

Division of Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Paul Cortland, IE

(301) 492-4175 Attachment: List of Recently Issued IE Information Notices

• See Previous Concurrences

a

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IN 87-XX

March, 1987 inserted or withdrawn to compensate for various reactivity changes during

operation of the reactor and can trip to provide shutdown capability. The

shutdown RCCAs are fully withdrawn from the core when the reactor is critical.

At Kewaunee, marks of fretting wear were found adjacent to the guide blocks

that position the rods when the RCCAs are in their withdrawn position. The 1- in.-thick stainless steel blocks are spaced on 12-in. centers and each rod in

the cluster passes through all eight of the blocks. At Point Beach the tubing

wore in two modes: sliding of the rods over the guide blocks during rod motion

and fretting. Five RCCAs at Haddam Neck had wall thinning resulting from fret- ting and four of these were actually wearing into the absorber material. All

of the others had wear, but to a lesser extent.

The tubing was worn by fretting resulting from flow-induced vibratory contact

between the rods and the guide blocks during long periods of steady-state power

operation. Vibration is hydraulically induced by flow of the reactor coolant;

therefore it is a continuous process when the reactor coolant pumps are in

operation. In general, fretting wear was 1/2-in. long and included one-third

of the circumference of the rod. The depth varied with the amount of time the

RCCAs were in the withdrawn position. The worst measured depth of tubing

penetration from fretting wear was 65 percent of tubing thickness.

A significant amount of short hairline cracks at the lower extremity of the

tubing was observed near the end plug region of the rod. The cracks extended

axially for 4 in. and penetrated the stainless tubing. No circumferential

cracks were found. Examination of the cracks showed that irradiation-induced

swelling of the absorber was the principal cause of tensile stress in the

cladding, which resulted in cracking after substantial irradiation.

No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

Edward L. Jordan, Director

Division of Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Paul Cortland, IE

(301) 492-4175 Attachment: List of Recently Issued IE Information Notices

• See Previous Concurrences D:DEER:fI

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02/18/87 03/i /87 03/02/87 03/ /87 03/ /87 03/ /87

IN 87-XX

February, 1987 during

inserted or withdrawn to compensate for various reactivity changes The

operation of the reactor and can trip to provide shutdown capability. is critical.

shutdown RCCAs are fully withdrawn from the core when the reactor

blocks

At Kewaunee, marks of fretting wear were found adjacent to the guide The 1 that position the rods when the RCCAs are in their withdrawn position.

and each rod in

in. thick stainless steel blocks are spaced on 12 in. centers tubing wore

the cluster passes through all 8 of the blocks. At Point Beach the

motion and

in two modes: sliding of the rods over the guide blocks during rod from fretting

fretting. Five RCCAs at Haddam Neck had wall thinning resulting

material. All of the

and four of these were actually wearing into the absorber

others had wear, but to a lesser extent.

contact

The tubing was worn by fretting resulting from flow-induced vibratory power

between the rods and the guide blocks during long periods of steady-state

flow of the reactor coolant;

operation. Vibration is hydraulically induced by are in

therefore it is a continuous process when the reactor coolant pumps one-third

operation. In general, fretting wear was 1/2-in. long and included

time the

of the circumference of the rod. The depth varied with the amount of

measured depth of tubing

RCCAs were in the withdrawn position. The worst

penetration from fretting wear was 65 percent of tubing thickness.

of the

A significant amount of short hairline cracks at the lower extremity extended

tubing was observed near the end plug region of the rod. The cracks

axially for 4 in. and penetrated the stainless tubing. No circumferential

cracks were found. Examination of the cracks showed that irradiation-induced the

swelling of the absorber was the principal cause of tensile stress in

cladding, which resulted in cracking after substantial irradiation.

notice.

No specific action or written response is required by this information

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

Edward L. Jordan, Director

Division of Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Paul Cortland, IE

(301) 492-4175 Attachment: List of Recently Issued IE Information Notices

D:DEPER:IE

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